Return-Path: Received: from hermes30.mail.cornell.edu (hermes30.mail.cornell.edu [132.236.56.55]) by lnscu5.lns.cornell.edu (8.13.6/8.13.6) with ESMTP id m2584GnS010951 for ; Wed, 5 Mar 2008 03:04:16 -0500 (EST) Received: from orchid.mail.cornell.edu (orchid.mail.cornell.edu [132.236.56.61]) by hermes30.mail.cornell.edu (8.13.6/8.13.6) with ESMTP id m2584GaK007017 for ; Wed, 5 Mar 2008 03:04:16 -0500 (EST) Received: (from daemon@localhost) by orchid.mail.cornell.edu (8.13.6/8.12.6) id m2584GKK004225 for palmer@mail.lns.cornell.edu; Wed, 5 Mar 2008 03:04:16 -0500 (EST) Received: from aps.anl.gov (router4_tc [10.236.56.17]) by orchid.mail.cornell.edu (8.13.6/8.12.6) with SMTP id m257xQWN001550 for map36@cornell.edu; Wed, 5 Mar 2008 03:04:15 -0500 (EST) Received: from aps.anl.gov (hestia.aps.anl.gov [164.54.98.20]) by 132.236.56.17; Wed, 5 Mar 2008 03:04:15 -0500 Received: from ([164.54.50.61]) by hestia.aps.anl.gov with SMTP id 4440338.12053729; Wed, 05 Mar 2008 02:03:57 -0600 Received: from alipes.aps.anl.gov (alipes [164.54.49.255]) by herald.aps.anl.gov (8.13.7/8.13.7) with ESMTP id m2583BYu012208; Wed, 5 Mar 2008 02:03:11 -0600 (CST) Received: from [164.54.62.43] (visa43.aps.anl.gov [164.54.62.43]) by alipes.aps.anl.gov (8.13.8+Sun/8.12.9) with ESMTP id m2583tUH023249; Wed, 5 Mar 2008 02:03:55 -0600 (CST) Subject: Re: This Week's Damping Ring Discussions at the Sendai GDE Meeting X-PH: V4.1@orchid From: Louis Emery To: "Mark A. Palmer" Cc: ilcdr@lbl.gov In-Reply-To: <47CD13B2.9000609@cornell.edu> References: <47CB6B12.5040200@cornell.edu> <47CD13B2.9000609@cornell.edu> Content-Type: text/plain Date: Wed, 05 Mar 2008 01:58:21 -0600 Message-Id: <1204703901.3521.100.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.10.3 (2.10.3-7.fc7) Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-301.8 required=500.0 tests=ALL_TRUSTED,FROM_ALIPES, FROM_APS,FROM_HERALD,USER_IN_ALL_SPAM_TO,USER_IN_WHITELIST autolearn=unavailable version=3.1.3 X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on herald.aps.anl.gov X-Original-IP: 164.54.98.20 X-Original-Hostname: hestia.aps.anl.gov X-PMX-Version: 5.2.2.285561, Antispam-Engine: 2.5.0.283055, Antispam-Data: 2008.3.4.234752 X-PMX-CORNELL-SPAM-CHECKED: orchid X-DCC-CULNS-Metrics: lnscu5.lns.cornell.edu 9999; Body=1 Fuz1=1 Fuz2=1 To all, I agree with the relative scores in the tables. I would weight the first table more. But I think it would not change the order of the results. I'm leaning towards the DCO cell structure because of the reduced number of magnets, and I think the DA problem is not insurmountable. I missed the webex session on Tuesday, so I have some comments and questions: I'm not sure how the DCO lattice at 100 degrees/cell ended up with a (much?) smaller dynamic aperture than the FODO5 lattice with 108 degree per cell. I see that the cell length for DCO is shorter (making the dispersion smaller) than the FODO5 FODO cell, perhaps to partially compensate the larger I5 created by the shorter and stronger dipole. I think the dynamic acceptance of FODO cells with constant circumference should scale roughly as the cell length squared. So a shorter dipole magnet resulted in a smaller dynamic aperture. Andy, was using a 2x field in the dipole for reducing the total dipole magnet cost? Could the magnet be longer without disrupting the mechanical layout much? To rephrase a point by Aimin, if maintaining a 90 degree phase advance is important for dynamic aperture, then an "upgrade" of momentum compaction from 1.7e-4 to a value 25% lower can be done with the conversion of the DCO cell to a TME-cell (keeping 90 degree cell) by the insertion of one quad. This is, of course, at a cost of 192 magnets. How does the lower symmetry of the DCO lattice affect the dynamic aperture? Could we have the superconducting stuff together in two groups at a 90 degree azimuth relative to the injection and extraction (like FODO4 but with doglegs added to reduce heat load)? Thanks. Louis Emery